The use of deep learning to achieve automated software vulnerability detection has been a longstanding interest within the software security community. These deep vulnerability detectors are mostly trained in a supervised manner, which heavily relies on large-scale, high-quality vulnerability datasets. However, the vulnerability datasets used to train deep vulnerability detectors frequently exhibit class imbalance due to the inherent nature of vulnerability data, where vulnerable cases are significantly rarer than non-vulnerable cases. This imbalance adversely affects the effectiveness of these detectors. A promising solution to address the class imbalance problem is to artificially generate vulnerable samples to enhance vulnerability datasets, yet existing vulnerability generation techniques are not satisfactory due to their inadequate representation of real-world vulnerabilities or their reliance on large-scale vulnerable samples for training the generation model.

This paper proposes GVI, a novel approach aimed at generating vulnerable samples to boost deep vulnerability detectors. GVI takes inspiration from human learning with imagination and proposes exploring LLMs to imagine and create new, informative vulnerable samples from given seed vulnerabilities. Specifically, we design a Chain-of-Thought inspired prompt in GVI that instructs the LLMs to first analyze the seed to retrieve attributes related to vulnerabilities and then generate a set of vulnerabilities based on the seed’s attributes. Our extensive experiments on three vulnerability datasets (i.e., Devign, ReVeal, and BigVul) and across three deep vulnerability detectors (i.e., Devign, ReVeal, and LineVul) demonstrate that the vulnerable samples generated by GVI are not only more accurate but also more effective in enhancing the performance of deep vulnerability detectors.